Seiche-Induced Mixing: Its Impact on Lake Productivity

Analysis of temperature and oxygen data at an inshore station in Lake Kinneret (Israel) indicates that cross-isopycnal mixing occurs at the littoral zone as a consequence of seiche activity. We suggest that near-botton mixing at the lake periphery is highly important for nutrient supply from the hypolimnion to the epilimnion. Temperature and temperature gradient distribution patterns along a cross-lake transect indicate horizontal transport via the metalimnion of the mixed water from the littoral toward deeper parts of the lake. Inshore localization of mixing and dilution of the mixed water during its transport cause the hypolimnetic water supply into the epilimnion to be higher nearshore than in the middle of the lake. Addition (5-10%) of hypolimnetic water to epilimnetic water in laboratory experiments results in enhanced primary production and increased algal biomass. The stimulating effect of hypolimnetic water on primary producers (algae) and the deduced pattern of nutrient-rich hypolimnetic water supply are consistent with observed spatial distributions of algae and fish (mainly planktivorous), which are more abundant in the lake periphery. We suggest that the import of hypolimnetic waters into the epilimnion enhances biological productivity of the lake.